private void btn_add_Click(object sender, RoutedEventArgs e)
        {
            if (!this.checkFields())
            {
                return;
            }
            //this.listBox.ItemsSource = null;
            StudentAddressBook obj = new StudentAddressBook(this.txtBox_firstName.Text, this.txtBox_lastName.Text, this.txtBox_company.Text,
                                                            this.txtBox_jobTitle.Text, this.txtBox_email.Text, this.txtBox_address.Text, this.txtBox_phCountryCode.Text, this.txtBox_ph.Text, this.txtBox_photoAddress.Text);

            this.listBox.Items.Add(obj);
            //this.listBox.Items.Remove();
            AddressBook.list.Add(obj);
            this.listBox.Items.Refresh();
            MessageBox.Show("Successfully ADDED");
        }
        private void btn_update_Click(object sender, RoutedEventArgs e)
        {
            if (!this.checkFields())
            {
                return;
            }
            StudentAddressBook obj = (StudentAddressBook)this.listBox.SelectedItem;

            obj.FirstName        = this.txtBox_firstName.Text;
            obj.LastName         = this.txtBox_lastName.Text;
            obj.CompanyName      = this.txtBox_company.Text;
            obj.JobTitle         = this.txtBox_jobTitle.Text;
            obj.Email            = this.txtBox_email.Text;
            obj.Address          = this.txtBox_address.Text;
            obj.CountryCode      = this.txtBox_phCountryCode.Text;
            obj.PhNumber         = this.txtBox_ph.Text;
            obj.Photo            = this.txtBox_photoAddress.Text;
            this.img_user.Source = null;
            this.listBox.Items.Refresh();
            MessageBox.Show("Successfully UPDATED");
        }